1. Field of the Invention
The present invention relates to seals, and, more particularly, to dynamic seals.
2. Description of the Related Art
A seal is a structure included in devices to prevent media from flowing past the seal into other areas of the device. Seals come in a great variety of shapes and sizes, depending on their intended application(s). One type of seal is a rotary seal, which is used in rotary applications. Such seals are disposed around a rotating element, such as a shaft, and create a seal around the rotating element. Another type of seal is a linear seal, which is used in linear applications. Such seals are disposed around a reciprocating element, such as a shaft, and create a seal around the reciprocating element.
When designing rotary and linear seals, durability of the seal is an importance design consideration due to the need for consistent performance of the seal throughout the lifetime of the seal. If the shape of the seal is altered due to damage from frictional heat or abrasion, a leak path may be formed that will allow the undesirable flow of media past the seal. Such damage typically requires the seal to be replaced, which can be an expensive and time-consuming endeavor if the seal is located in an environment that requires a significant amount of disassembly to access.
Another cause of seal damage and failure that negatively impacts seal performance can be caused by extrusion of the seal material during operation. As is known, sealing environments typically have a clearance formed between the sealed element and the hardware adjacent to the location of the seal, which can be placed in a groove formed in the hardware, that is referred to as an extrusion gap. During operation of the hardware, differential pressures can cause the seal to be forced against the groove of the hardware and deform the material of the seal. If sufficiently forced, the seal material can be overly deformed into the extrusion gap and damaged due to abrasion. Once the differential pressure is removed, the seal returns to its original shape minus any seal material that abraded away due to extrusion, which can lead to loss of compression of the seal and a leak path being formed. Further, damage that arises due to extrusion can compound throughout the life of the seal to progressively abrade away larger portions of the seal material. Attempts to reduce the damage caused by extrusion have included using sealing materials with higher hardness modulus and/or wider dynamic sealing lips, which reduces the design flexibility of seals and can result in significant friction at the dynamic sealing interface that hampers the function of the sealing element and can create excessive heat that will damage the seal.
Another consideration that plays an important part in the design of dynamic seals is the shape of the hardware and moving element that are to be sealed. Particularly, sealing elements that are curved or non-round can present a challenge due to an asymmetrical or irregular shape that is difficult to properly seal and prevent leakage. Specifically, these shapes do not have a constant clearance, relative to the hardware, across the length of the shape. The non-constant clearance makes it difficult to form a continuous seal around the entirety of the element, especially if the element moves.
What is needed in the art is a seal that can be used to continuously seal curved or non-round elements.